1. Field of the Invention
The present invention relates to a testing device of integrated circuit and more particularly, to a probe card capable of maintaining horizontal of the probe assembly.
2. Description of the Related Art
Integrated circuits on a wafer have to pass electrical test and those passing the test are picked out for the following package procedure to form chips. The chips are tested again to pick out defective products. In the rear-end process of integrated circuit, there are several testing procedures of the electrical properties of the integrated circuits or chips. In the present electrical test, a probe card is provided which includes several probes contacted with the circuits for testing its electrical properties.
In the electrical test, planes on tips of the probes has to be substantially parallel to planes of pads of the integrated circuit that causes the probes with the same pressure press the pads of the integrated circuit to build a well electrical connection between the probe card and the integrated circuit. It may not build an electrical connection between the probe card and the integrated circuit while the probes with different pressures pressed the pads that makes the probe card can not read the actual electrical properties of the integrated circuit.
The probes are flexible to make parallel between the probes of the probe card and the pads of the integrated circuit, except that the probe card usually is provided with an elastic device to support an electrical signal transform board, on which the probes are provided, for prevention of a difference in height when the electrical signal transform board inclines. Such device was taught in US 2004/0104738, which provides a spring between the electrical signal transform board and a circuit board to prevent the height difference of the electrical signal transform board. It must leave a space between the electrical signal transform board and the circuit board for the spring that increases the size of the probe card and make a loose structure of components. Types of the spring are limited because the spring is between the electrical signal transform board and the circuit board. In addition, a distance between the circuit board and each probes is increased that limits an flexible adjustment of client's products.